A problem of dissipating heat generated within an integrated circuit and of maintaining an internal temperature of a package below a maximum tolerable value is particularly relevant when assembling power device packages on the surface of a printed circuit board. Such power device packages are typically formed from a plastic material. These power device packages include a body of resin that partially encapsulates a metal heat sink which acts as an internal heat sink. The metal heat sink is usually made of copper.
A silicon chip or die of an integrated circuit is mounted on the surface of the internal heat sink. According to a typical geometry of many of these power device packages, the presence of the metal heat sink on a bottom face of the integrated device makes it impossible to install an external heat sink that simply rests on the device when mounted on the printed circuit board because of the relatively poor thermal coupling formed.
To increase heat dissipation during operation, several approaches are known. A first approach is to pattern a copper pad on the printed circuit board onto which the internal heat sink of the power device package is soldered. In this manner, the heat generated inside the device may be effectively transferred through the copper pad. Accordingly, the heat is spread out over the printed circuit board.
Often, a plurality of holes are formed within the copper pad. These holes have their inner wall covered with a film of copper, and comprise as many conductive vias as necessary for transferring heat across the thickness of the board to the other side where another dedicated copper pad may be patterned. On the copper pad, an external metal sink may be placed or contact is made by the metal chassis of the apparatus.
According to a similar approach, the metal coated holes do not cross the entire thickness of the board, but reach a ground metallization layer sandwiched therein. The ground metalization layer is typically in the form of a copper film, which disperses the heat throughout the board. Yet another approach includes using printed circuit boards specially formed on a relatively thick metal substrate of a thermally conductive material, such as aluminum.
All of these approaches imply the use of specially configured printed circuit boards, or the use of printed circuit boards having special composite structures for heat dissipation. Therefore, these known approaches are rather costly, and often require special printed circuit boards that may not be compatible with a particular manufacturer's requirements.